Enhancing Lithium-Oxygen Battery Performance by Optimizing the Interaction of Cathode Materials and Soluble FePc...

Macrocyclic redox mediators (RMs) such as iron(II) phthalocyanine (FePc) can improve lithium-oxygen (Li─O₂) battery performance by shuttling electrons and oxygen. However, their low solubility in electrolytes due to strong π-π interaction with carbon-based cathodes (e.g., 3D graphene) limits practical applications. Herein, non-sp²-carbon materials (MoN, TiN, and Ti₃C₂T_x) are employed as cathodes to regulate cathode-FePc interactions, thereby increasing FePc solubility and improving Li─O₂ battery performance. For cathode-FePc coupling catalysts, the solubility of FePc rises as its adsorption strength on cathodes (3DG, MoN, TiN, and Ti₃C₂T_x) decreases, creating a "volcano-shaped" correlation with cathode-FePc@battery performances. Correspondingly, the total resistance (R_ESR = R_s + R_ct) of the batteries after charging exhibits an "inverted-volcano" trend. The optimized TiN-FePc catalyst achieves the highest cycling stability (392 cycles). Control experiments and density functional theory (DFT) calculations demonstrate that TiN-FePc catalyst maintains high FePc concentration in electrolyte while facilitating electron transfer and oxygen shuttling, significantly enhancing catalytic activity. This work provides an efficient strategy for designing high-performance Li─O₂ batteries by optimizing RMs-cathode interactions.